settings for gaming?

[eilif]

I've never gamed it, but based on your requirements I think that Firefly/Serenity might actually be the best good choice. No aliens, but you've got at least 4 major factions and probably some minor ones. Reavers, independent operators of various types (like the firefly crew), Browncoats (rebels in light gear, brown uniforms), Alliance (bad guy troopers, well equipped, body armor).  There are also various settler groups underworld types and security operations in the series too that could be their own factions.

IIRC, it has had a couple RPG publications to expand a bit beyond the series and movie.  So it wouldn't be too hard to take it all in, but there's enough background material for a good gaming universe.  For miniatures, if you decide to go specific to the firefly crew, there's a number of "not" versions of them, but there's lots of other options that could work for them and the other factions. Lastly, it's still relatively popular among sci-fi fans so your group might get into it more easily.

My last suggestion, would be to go with a faction that excites both you and your friend. Even if it ticks all the boxes, if it doesn't get both of you fired up, then it's not the best choice.

Best of luck whatever you decide.